This invention relates to polyether polyols prepared by alkoxylation of cashew nutshell liquid (CNSL), a renewable resource material, to the process for the preparation of these polyether polyols, to flexible foams produced from these long chain polyether polyols, and to a process for the production of these foams.
Polyurethane foams have found extensive use in a multitude of industrial and consumer applications. This popularity is due to the wide ranging mechanical properties of polyurethane combined with its ability to be relatively easily manufactured. Automobiles, for example, contain numerous polyurethane components, such as seats, dashboards and other cabin interior parts. Polyurethane foams have traditionally been categorized as being flexible, semi-rigid or rigid; with flexible foams generally being softer, less dense, more pliable and more subject to structural rebound subsequent to loading than are rigid foams. Most flexible polyurethanes foams in commerce are produced by either a free-rise (slabstock) or molded process.
The production of polyurethane foams is well known to those skilled in the art. Polyurethanes are formed from the reaction of NCO groups with hydroxyl groups. The most common method of polyurethane production is via the reaction of a polyol and a polyisocyanate which forms the backbone urethane group. A blowing agent is also included in the formulation along with a surface active agent to generate the characteristic cellular structure of the polyurethane foam. Most flexible polyurethane foam formulations contain water as an isocyanate reactive component to chemically form carbon dioxide as a blowing agent and an amine moiety which reacts further with the polyisocyanate to form urea backbone groups within the polymer. These urethane-urea polymers are also included under the broad definition of polyurethanes. Cross-linking agents, blowing agents, flame retardants, catalysts and other additives may also be included in the polyurethane formulation as needed.
Polyols used in the production of polyurethanes are typically petrochemical in origin, being generally derived from propylene oxide, ethylene oxide and various starters such as propylene glycol, glycerin, sucrose and sorbitol. Polyester polyols and polyether polyols are the most common polyols used in polyurethane production. For flexible foams, polyester or polyether polyols with molecular weights of from about 2,000 to 10,000 are generally used, whereas for rigid and semirigid foams, shorter chain polyols with molecular weights of from about 400 to 2,000 are typically used. Polyester and polyether polyols can be selected to allow the engineering of a particular polyurethane foam having desired final toughness, durability, density, flexibility, compression ratios and modulus and hardness qualities. Generally, higher molecular weight polyols and lower functionality polyols tend to produce more flexible foams than do lower molecular weight polyols and higher functionality polyols.
Petroleum-derived components such as polyester and polyether polyols pose several disadvantages. Use of such polyester or polyether polyols contributes to the depletion of petroleum-derived oil, which is a non-renewable resource. Also, the production of a polyol requires the investment of a great deal of energy because the oil needed to make the polyol must be drilled, extracted and transported to a refinery where it is refined and processed to purified hydrocarbons that are subsequently converted to alkoxides and finally to the finished polyols. As the consuming public becomes increasingly aware of the environmental impact of this production chain, consumer demand for “greener” products will continue to grow. To help reduce the depletion of petroleum-derived oil whilst satisfying this increasing consumer demand, it would be advantageous to partially or wholly replace petroleum-derived polyester or polyether polyols used in the production of polyurethane foams with renewable and more environmentally responsible components.
Attempts have been made by workers in the art to accomplish the replacement of petroleum-derived polyols with components derived from renewable resources. Plastics and foams made using fatty acid triglycerides derived from vegetable oils, including castor oil, sunflower oil, canola oil, linseed oil, cottonseed oil, corn oil, poppy seed oil, peanut oil and soybean oil and derivative of these, have been developed. With increased interest in renewable, versatile, and environmentally-friendly resources, cashew nutshell liquid (CNSL) is also gaining attention as a potential ingredient for plastics manufacture.
Various investigations and uses of cashew nutshell liquid and/or cashew nutshell oil are described in, for example, U.S. Pat. Nos. 1,725,791, 2,317,585, 2,470,808, 2,758,986, and 4,233,194; were reported by A. Strocchi and G. Lercker in the article “Cardanol in Germ and Seed Oils Extracted from Cashew Nuts Obtained by the Oltremare Process” in Journal of the American Oil Chemists' Society, Vol. 56, June 1979, pp. 616-619; and by Patrick T. Izzo and Charles R. Dawson in the article “Cashew Nut Shell Liquid. VII. The Higher Olefinic Components of Cardanol” in Journal of Organic Chemistry, Vol. 15, 1950, pp. 707-714.
More recently, cashew nutshell liquid has been investigated as a potential monomer source for producing polymeric materials. See, for example, the paper by C. K. S. Pillai titled “Polymeric Materials from Renewable Resources: High Value Polymers from Cashewnut Shell Liquid” presented at the 4th International Plastics Exhibition & Conference, Popular Plastics and Packaging, Plastindia Exhibition Special Issue, 2000, pp. 79-90.
Various compositions can be produced from cardanol as described in JP48029530 and WO 92/21741. JP48029530 discloses reacting an aldehyde condensate of CNSL or cardanol or aldehyde cocondensate with ethylene oxide or propylene oxide to form an oxyetherified substance which can be reacted with a diisocyanate to form a quick-dry coating composition. WO 92/21741 describes aqueous cleaning compositions comprising mixtures of cardanol ethoxylation products. U.S. Pat. No. 6,229,054 describes derivatives of cardanol formed by hydroxyalkylation with cyclic organic carbonates.
A new class of polyols from cardanol which are suitable for the production of polyurethanes are described by Kattimattahu I. Suresh and Vadi S. Kishanprasad in the article “Synthesis, Structure, and Properties of Novel Polyols from Cardanol and Developed Polyurethanes” in Industrial & Engineering Chemistry Research (2005), 44(13), pp. 4504-4512. Also, see WO 2006/003668A1 and U.S. Published patent application U.S. 2006/004115 A1, which are believed to be equivalents. These published patents describe these polyols and the production of polyurethanes from such polyols.
Other polymers based on the oil of CNSO (cashew nutshell oil) are disclosed in U.S. Pat. No. 6,051,623. These products are formed from CNSO and diisocyanates or polyisocyanates. The CNSO is a mixture of a biphenol and a fatty acid, the NCO group of the isocyanates can react with the COOH of the fatty acid, the OH of the phenyl radicals or the double bonds of the chains. The resultant products are rigid foamed plastic materials.
DE 10004427 described polyurethanes produced from polyisocyanates and CNSL in which the double bonds are at least partially saturated by the reaction with sulfur or peroxides under heating. These CNSL products may be mixed with other polyols and/or soybean oil and reacted with polyisocyanates to form hard plastic products.
Hydrophobic polyols of low viscosity which are prepared by reacting a mixture having an OH number of 180 to 300, a viscosity at 23° C. of 5000 to 20,000 mPa·s and an OH functionality of 2.8 to 4.5 are disclosed in U.S. Published patent application 2005/0192423 A1. This mixture of cardanol-depleted cashew-nutshell liquid (CNSL) is reacted with alkylene oxides to form hydrophobic polyols which can be reacted with polyisocyanates to form polyurethane systems that are suitable as coatings, adhesives, sealants or molding compounds.
It has now been discovered that polyether polyols derived from cashew nutshell liquid can be produced which are suitable for the production of flexible polyurethane foams. Unlike polyether polyols derived from vegetable oil based polyols, the CNSL polyols can be alkoxylated in the presence of strongly alkaline catalysts without substantially degrading the initiating polyol. This facilitates the formation of poly(oxyethylene) capped polyether polyols having high primary hydroxyl content, which are desirable for flexible foam processing; especially molded foam.